Method of forming a roving ball of non-twisted roving



March 28, 1967 w. R. STEITZ ETAL 3,311,518

METHOD OF FORMING A ROVING BALL OF NON-TWISTED ROVING Filed Dec. 6', 1963 INVENTOR WILLIAM R. STEITZ HARRY TALV ATTORNEY United States Patent 3,311,518 METHOD OF FORMHNG A ROVING BALL 0F NON-TWISTED ROVING William R. Steitz and Harry Talv, Nashville, Tenn., as-

signors to Ferro Corporation, Cleveland, Ohio Filed Dec. 6, 1963, Ser. No. 328,722 Claims. (Cl. 156-148) This invention details generally with a method for winding linear material into a helix, and deals more particularly with a method for winding roving into a roving ball in such a manner that roving drawn from the interior of said ball will exhibit minimum twist.

As is well known in the field of fiber glass, and particularly in the field of filament winding thereof, individual filaments are drawn from a molten supply of glass, and rapidly wound onto a cake package at extremely high speeds to thus form a strand. This preliminary operation is described in United States Patents 2,391,870, 2,433,304 and 2,457,786.

These cake packages are later supported on a creel rack, strands respectively from a number of cake packages are converged together at high speed, and wound onto a cylindrical mandrel to form a cylindrically shaped roving ball, which roving ball has wide application in any number of subsequent fiber glass operations, such as supplying roving for mat machines, wherein the roving from the roving ball is chopped into short lengths and cascaded onto a moving belt to form a felted mat; for continuous weaving or said roving into coarse woven cloth for plastic reinforcement; or for winding of said roving in substantially continuous lengths about forming mandrels for the production of fiber glass reinforced, filament wound, pressure vessels and the like.

For an illustration of the application of roving to a filament winding operation, said roving being applied by inside takeoff from the roving ball, refer to US. Patent 2,718,583.

As is well known, the convergence of a multiplicity of strands and/or filaments, over a flat guide, to form a roving, disposes the multiplicity of strands in a relatively flat band. This band is then directed onto a rapidly rotating cylindrical winding mandrel, the roving as it is applied to the winding mandrel being reciprocated back and forth according to a predetermined cycle in order to produce a cylindrical roving ball having distinct and uniform way wind characteristics.

In the field of filament winding for applying continuous roving to a forming mandrel for later impregnation with a thermosetting resin, or for that matter in applying a preimpregnated roving to a forming mandrel for ultimate thermosetting of the resin, to form a pressure vessel, optimum strength will not be achieved if the roving as applied to the forming mandrel is not laid on in the form of a fiat, untwisted band. That is, if there is a twist in roving as it is laid onto a forming mandrel, it tends to create air voids or resin rich areas in the ultimate laminate, and also tends to create a variation in the concentration of fiber per unit cross-sectional area of the laminate, thereby causing a reduction in strength in some areas.

However, under the practice followed heretofore, it has been practically impossible to take roving from a stationary, non-rotating roving ball, and lay it onto a forming mandrel without imparting a twist thereto. The reason for this is that a roving ball essentially is a series of overlapped, helical windings. By analogy, if a ribbon of paper is wrapped around ones thumb, the outside end of said ribbon of paper being held firmly after the winding has been completed, and the inside end of said winding is pulled from the cylinder thus formed in either direction out of either the center of the winding or the outside thereof, there will be a very definite twist imparted to the ribbon. This is substantially what happens to the roving in a roving ball. It is therefore an object of this invention to provide a method for producing a substantially continuous multifilament length from a non-rotating helical winding thereof characterized by said substantially continuous length exhibiting minimum twist as drawn from said helical winding thereof.

It is yet another object of this invention to provide a method for achieving a filament wound article wherein the filaments in any given substantially continuous length reside in substantially parallel, non-twisted relationship.

It is yet another object of this invention to provide a substantially continuous multifilament length from a helical winding thereof, said substantially continuous length having been impregnated with a bonding resin, said substantially continuous length exhibiting a minimum of twist as drawn from said helical winding thereof.

It is yet another object of this invention to provide a filament wound article which is the product of being formed from a preimpregnated, substantially continuous multifilament length of said filaments, any given length of which is characterized by a substantially parallel, nontwisted relationship.

One way to eliminate the objectionable twist to roving as taken from a roving ball for application. in filament winding is to mount the roving ball on a spindle and, instead of taking the roving from the roving ball while it is held stationary, pulling it from the ball in precisely the reverse manner from which it is was applied while the ball is spun about its axis.

However, this method has a number of disadvantages. In the first place, outside unwinding takeoff from a spinning roving ball would necessitate spinning the ball at extremely high speeds in order to feed roving therefrom at the high rates required for filament winding, which in turn presents problems in braking if it should become desirable to suddenly stop the feed; in this situation, the mass of the roving ball in motion must be quickly brought to a halt, otherwise the roving would literally backlash and form a tangle of many hundreds of feet during the period the roving ball is in motion and the slack in the roving is not being taken up. Too, outside takeoff means extra equipment in the form of spindles, etc.

Also the inertial force required to start the'ball rotating creates design problems when building a filament winding machine, especially when many roving substantially continuous lengths are used simultaneously.

It is therefore quite apparent that inside or outside takeoff from a non-rotating ball is much to be preferred inasmuch as any sudden cessation in the motion of roving as being pulled from the roving ball causes no problems in override, since the mass of the individual length of roving being pulled from the interior of the stationary ball is slight and has very little tendency to continue in motion once the pulling tension has been relaxed; the only drawback to such takeoff heretofore being the undesirable twist.

Briefly and simply stated, our invention consists in forming a roving ball wherein the roving has a built-in compensatory twist of just the right magnitude so that, when roving is pulled from the interior of the roving ball at a high rate of speed, no objectionable twist will be present.

Proceeding now to a detailed description of our inven tion, attention is directed to the attached drawings, wherein:

FIG. 1 is a simplified, schematic diagram illustrating the principle of our invention.

FIG. 2 illustrates generally a roving ball on a winding mandrel.

For simplicity of illustration, roving, as wound on a roving ball, is shown as a simple helix of about three convolutions in FIG. 1. As can readily be visualized, each single convolution of the ribbon-like roving illustrated would of course be multiplied many thousands of times in a roving ball.

In FIG. 1, the first end of the ribbon-like roving 1 which comes in direct contact with the winding mandrel will be referred to as the leading end and is designated by reference numeral 2. The outside, or tail end of the roving as formed into a roving ball, will be referred to as the trailing end, and is represented by reference numeral 3.

It is to be understood of course that trailing end 3 would not necessarily appear at the opposite end of a roving ball from leading end 2, either may occur at any point in the length of the ball.

As hereinbefore described, as a multiplicity of filaments are converged and wound onto a cylindrical mandrel to form a roving ball, they lay onto the mandrel generally in the form of a flat band, or ribbon, generally represented by reference numeral 1 in FIG. 1. As the roving reposes in the roving ball, it is of course in fiat, ribbonlike form, and the filaments are in substantially parallel non-twisted relationship with respect to each other.

However, assuming the helix in FIG. 1 to represent a roving ball, it will become readily apparent that, if trailing end 3 is held fast, as it normally would be in removing roving from a roving ball inside takeoff, whether leading end 2 is pulled outwardly from the center of the roving ball in either direction 4, or 5, a distinct twist will be imparted to the roving; the twist imparted through inside takeofi from the first helix hereinafter referred to as a first order twist.

However, if roving 1 as stretched to its length from the helix illustrated, maintaining the first order twist thus imparted, is then wound in such a manner that the same leading end maintains its lead position, into a second helical winding, the direction of wind being substantially the same as the first wind, then, after the second winding has taken place, the leading end is pulled from the interior of the cylinder thus formed in a direction opposite that from which it was originally pulled from the first helix to initiate rewinding, it will be seen that the twist in the ribbon has been materially reduced. If all conditions of the second winding have been substantially the same as the first winding, the twist will be practically eliminated. The twist imparted through inside takeoff from the second helical winding in a direction opposite to takeoff from the first winding, is a second order twist, and literally nullifies the existing first order twist to produce roving having virtually all twist eliminated.

It is very critical, in this particular embodiment, that the interior end be pulled from the opposite end of the second helical winding from the direction it was pulled from the first helical winding to wind the second. The reason for this is, that if the interior end is pulled from the second helical winding in the same direction as the first, the twist will be double that of the first as a second first order twist will be achieved.

Thus, in actual practice, roving is wound into a roving ball having a leading and trailing end respectively, the roving ball thus formed is then set up and the leading end pulled from the interior of the roving ball in either direction 4 or 5, and wound into a second helical winding from the first, all winding characteristics of the second helix, such as way wind, direction of rotation of the mandrel, etc., being maintained substantially the same as in the first helix.

There is thus produced a roving ball from which, if the roving is pulled from the interior in a direction opposite from that which said same end was pulled from the first helical winding to form the second, will produce a roving characterized by its component filaments lying in substantially parallel, non-twisted relationship. When referring to directions of pull of the leading end of the roving from first and second helical windings thereof, it is to be understood that the respective helixes are always viewed from the same relative position.

Substantially the same effect as that described above may be achieved by winding a first helix as described, pulling the leading end from the interior thereof in one direction and winding said roving into a second helix having an opposed winding direction to the first, then pulling the leading end from said second helix from the same end as the first to provide a substantially non-twisted roving.

By referring to a second helix as having an opposed winding direction to the first, is meant that, if, as the first winding was viewed while the mandrel turned clockwise, with respect to the position of the source of roving to be wound, the mandrel for winding the second helix would be rotated counterclockwise with respect to the position of the source of roving, and vice versa; the positions in space of the roving source, mandrel and observer remaining substantially unchanged with respect to the first and second windings.

In the alternate variation thus described, further definition of the respective ends is required. Thus, in utiliz' ing an opposed second winding the same ends of the first and second helixes must be referred to as the ends of said helixes when viewed, respectively, while the mandrel rotates clockwise for the first helical winding, and counterclockwise for the second, or yice versa. In the second variation thus described, the second order twist is also achieved in the second winding, but because the direction of Wind in the second helix has been reversed, the critical end of the second helix from which to pull the leading end of the roving to eliminate twist must be more clearly defined.

When all the winding characteristics are repeated substantially the same as in the first embodiment described above, the opposite ends of the respective helixes are those when each helix is viewed from the same position with respect to the direction of wind.

The roving ball thus formed is an article of commerce and may be sold to filament winders, mat manufacturers, etc.

In addition to the embodiment described above wherein the leading end is taken from the inside of the roving ball for subsequent rewinding, with the leading end taken from the second ball for direct application, there are in= stances wherein it would be preferable, while holding the roving ball stationary and in a non-rotating attitude, to pull the roving from the exterior of the ball, over one end thereof. It will be apparent that a twist is imparted to the roving when it is pulled from the exterior of a non-rotating ball and substantially the same procedure would be utilized as described above for producing a roving ball designed for outside takeoff of the roving therefrom without a twist, while the roving ball is maintained in a non-rotating attitude.

In the latter situation, trailing end 3 of the initially wound helix would be pulled over one end of said helix in either direction 4 or 5, trailing end 3 then becoming the leading end in a subsequently wound second helix with leading end 2 of the first helix assuming the position of trailing end 3 in the second helix. Thus, when trailing end 3 is pulled from the first helix from the outside thereof in direction 5, and rewound into a second roving ball having essentially the same winding characteristics as the first, then, in order to realize the compensatory effect of the twist first imparted, trailing end 3 of the second helix (formerly leading end 2) would have to be pulled from the exterior of the roving ball in the opposite direction, or in direction 4, in order to achieve a relatively flat band of roving.

Hence my invention is of such application that it applies to either outside or inside takeoff, so long as the roving ball (second helical winding) in final application is in a non-rotating attitude. Too, it is conceivable that various combinations of preliminary treatment of the roving, i.e., inside takeoff to establish twist in one direction prior to rewinding, then either inside or outside takeoff from the final roving ball in order to achieve the opposite twist to compensate for the first twist achieved.

Regardless of how it is achieved, our invention consists in establishing either a first or second order twist in a substantially continuous length of roving, while it reposes in the form of a second helical winding thereof, then pulling from said helical winding, while it reposes in a substantially non-rotating attitude, a roving end in a direction and manner as hereinbefore described, to impart a compensatory twist to that already existing in said roving as it reposes in said helical winding, which twist would be a second order twist if the roving reposes in a first order twist, or first order twist if the roving reposes in a second order twist.

Such roving may also very successfully be applied in a manner disclosed in US. Patent 2,718,583, to for-m a pressure vessel by the filament winding process, it being a matter of choice, and a process well known in the art, to either impregnate the filament wound form, after forming, with a suitable resin, usually a thermosetting polymerizable resin exemplified by the polyester resins, then curing same to form the finished filament wound reinforced article, to continually impregnate the roving with resin in a process step just before the forming of a part, or to preimpregnate the roving prior to winding it into a roving ball with any of the well-known resins currently employed for this purpose, then curing the preimpregnated resin on the forming mandrel to form a finished article such as that disclosed in US. Patent 2,718,583 or 3,031,099.

Having thus described our invention in accordance with the applicable rules of the United States Patent Office and Federal statutes relating thereto, we therefore claim:

1. The method of producing a substantially continuous multifilament length wherein the relationship of the component filaments within said substantially continuous length are characterized by minimum twist, from a first helically wound roving ball wherein said roving has a leading and trailing end, comprising the steps of:

(a) rewinding said roving from said first roving ball into a second helically Wound roving ball, maintaining the same end as leading end in said second roving ball,

(b) during step (a) imparting a first order twist to said roving as it is wound into said second roving ball,

(c) while maintaining said second roving ball in a nonrotating attitude, drawing said roving from said second roving ball by pulling said leading end therefrom,

(d) and simultaneously with step (c), applying a second order twist to said roving,

to thereby equalize its existing first order twist to provide a roving as removed by its leading end from a helical winding thereof, characterized by its component filaments lying in substantially parallel relationship and exhibiting minimum twist with respect to each other.

2. The method of producing a reinforced article from a substantially continuous multifilament length wherein the relationship of the component filaments within said substantially continuous length are characterized by minimum twist, from a first helically wound roving hall wherein said roving has a leading and trailing end, comprising the steps of:

(a) rewinding said roving from said first roving ball into a second helically wound roving ball, maintaining the same end as leading end in said second roving ball,

(b) during step (a) imparting a first order twist to said roving as it is wound into said second roving ball,

(0) while maintaining said second roving ball in a nonrotating attitude, drawing said roving from said sec- 6 ond roving ball by pulling said leading end therefrom,

(d) simultaneously with step (c), applying a second order twist to said roving,

(e) windingsaid roving, as provided by steps (c) and ((1) onto a forming mandrel,

(f) impregnating said winding produced by step (e), while on said mandrel, with a bonding resin and curing same,

to provide a reinforced article characterized by the filaments of its component reinforcing media lying in substantially non-twisted, substantially parallel relationship.

3. The method of producing a reinforced article from a substantially continuous multifilament length wherein the relationship of the component filaments within said substantially continuous length are characterized by minimum twist, from a first helically wound roving hall wherein said roving has a leading and trailing end and reposes within said roving ball in the form of a substantially nontwisted multifilament substantially continuous length and said roving has been preimpregnated with a bonding resin, comprising the steps of:

(a) rewinding said roving from said first roving ball into a second helically wound roving ball, maintaining the same end as leading end in said second roving ball,

(h) during step (a) imparting a first order twist to said roving as it is wound into said second roving ball,

(c) while maintaining said second roving ball in a nonrotating attitude, drawing said roving from said second roving ball by pulling said leading end therefrom,

(d) simultaneously with step (c), applying a second order twist to said roving,

(e) winding said roving as provided by steps (0) and (d) onto a forming mandrel,

(f) and while said winding produced by step (e) is on said forming mandrel, curing said bonding resin,

to provide a reinforced article characterized by the filaments of its component reinforcing media lying in substantially non-twisted, substantially parallel relationship.

4. The method of claim 1 wherein said roving in said second roving ball is preimpregnated during step (a) with a bonding resin.

5. The method of producing a substantially continuous multifilament length wherein the relationship of the component filaments within said substantially continuous length are characterized by minimum twist, from a first helically wound roving ball wherein said roving has a leading and trailing end, comprising the steps of:

(a) rewinding said roving from said first roving ball into a second helically wound roving ball, maintaining the same end as leading end in said second roving ball, but winding same into said second roving ball in a direction opposite to that in which it was wound in said first roving ball,

(b) during step (a) imparting a twist to said roving as it is wound into said second roving ball,

(c) drawing said roving from said second roving ball by pulling said leading end therefrom in the same direction as that from which it was drawn from said first roving ball,

((1) and simultaneously with step (c), applying a twist to said roving opposite to that imparted in step (b) above,

to thereby equalize its existing first order twist to provide a roving as removed by its leading end from a helical winding thereof, characterized by its component filaments lying in substantially parallel relationship and exhibiting minimum twist with respect to each other.

6. The method of claim 5 wherein the roving in said second helically wound roving is preimpregnated during step (a) with a bonding resin.

7. The method of producing a substantially continuous multifilament length of roving, wherein the relationship of the component filaments within said substantially continuous length are characterized by minimum twist, from a first helically wound roving ball wherein said roving has a leading and trailing end, comprising the steps of:

(a) rewinding said roving from said first roving ball into a second helically wound roving ball, using the trailing end of said first helically wound roving ball as the leading end in said second roving ball,

(b) during step (a) imparting a twist to said roving as it is wound into said second roving ball,

(c) while maintaining said second roving ball in a nonrotating attitude, drawing said roving from said second roving ball by pulling its trailing end therefrom in a direction opposite to that from which said trailing end was drawn from said first roving ball,

(d) and simultaneously with step (c), applying a twist to said roving opposite to that imparted in step (b),

to thereby equalize its existing twist to provide a roving as removed by its trailing end from a helical winding thereof, characterized by its component filaments lying in substantially parallel relationship and exhibiting minimum twist with respect to each other.

8. The method of claim 7 wherein the roving in said second helically wound roving ball is preirnpregnated dur ing step (a) with a bonding resin.

9. Method of producing a substantially continuous multifilarnent length from a helical winding thereof wherein the relationship of the component filaments within said substantially continuous length are characterized by minimum twist, comprising the steps of:

(a) advancing and converging a multiplicity of substantially continuous filaments into a multifilament length,

(b) winding said substantially continuous length into a first helical winding of same,

(c) pulling an end of said length from said first helical winding thereof and rewinding said substantially continuous length from said first helical winding into a second helical winding,

(d) concurrently with step (c) above, imparting a twist to said substantially continuous length,

(e) drawing an end of said roving from said second helical winding thereof while maintaining said second helical winding thereof in a non-rotating attitude,

(f) and concurrently with step (e) above, imparting to said substantially continuous length a twist opposite to that imparted in step ((1) above,

to thereby equalize said first twist to provide a substantially continuous multifil-ament length as drawn from said 5 helical winding, which substantially continuous length exhibits a minimum twist relationship between its component filaments.

10. Method of producing a substantially continuous multifilament length from a helical winding thereof wherein the relationship of the component filaments within said substantially continuous length are characterized by minimum twist, comprising the steps of:

(a) advancing and converging a multiplicity of substantially continuous filaments into a multifilament length, (b) winding said substantially continuous length into a first helical winding of same,

(c) pulling an end of said length from said first helical winding thereof and rewinding said substantially continuous length from said first helical winding into a second helical winding,

(cl) concurrently with step (c) above, imparting a twist to said substantially continuous length,

(6) drawing an end of said roving from said second helical winding thereof while maintaining said second helical winding thereof in a non-rotating attitude.

(f) concurrently with step (e) above, imparting to said substantially continuous length a twist opposite to that imparted in step (d) above,

(g) winding said substantially continuous length provided by step (f) onto a forming mandrel,

(h) and impregnating said winding produced by step (g), while on said mandrel, with a bonding resin and curing same,

to provide a reinforced article characterized by the filaments of its component reinforcing media lying in substantially non-twisted, substantially parallel relationship.

References Cited by the Examiner UNITED STATES PATENTS EARL M. BERGERT, Primary Examiner.

P. DIER, Assistant Examiner, 

1. THE METHOD OF PRODUCING A SUBSTANTIALLY CONTINUOUS MULTIFILAMENT LENGTH WHEREIN THE RELATIONSHIP OF THE COMPONENT FILAMENTS WITHIN SAID SUBSTANTIUALLY CONTINUOUS LENGTH ARE CHARACTERIZED BY MINIMUN TWIST, FROM A FIRST HELICALLY WOUND ROVING BALL WHEREIN SAID ROVING HAS A LEADING AND TRAILING END, COMPRISING THE STEPS OF: (A) REWINDING SAID ROVING FROM SAID FIRST ROVING BALL INTO A SECOND HELICALLY WOUND ROVING BALL, MAINTAINING THE SAME END AS LEADING END IN SAID SECOND ROVING BALL, (B) DURING STEP (A) IMPARTING A FIRST ORDER TWIST TO SAID ROVING AS IT IS WOUND INTO SAID SECOND ROVING BALL, (C) WHILE MAINTAINING SAID SECOND ROVING BALL IN A NONROTATING ATTITUDE, DRAWING SAID ROVING FROM SAID SECOND ROVING BALL BY PULLING SAID LEADING END THEREFROM, 